Suppose a person(who doesn't do any sports) changes a diet, so that it has a "right" ratio of protein, carbs and fats, and a small carbs deficit. What will happen next? will he lose fat or muscle or both?

2 Answers 2


What do you mean by carb deficit? There is no carb requirement level that you can be over or under. You can eat 80% carbs or 0% carbs and be fine.

If your total intake of calories is less than your total calorie use, you will burn fat, even if you lie in bed all day.

Wether you lose fat or muscle depends on your current amount of muscle, on your level of exercise, on your genes and on your calorie deficit. Having a lot of muscle mass makes it harder to maintain it, more exercise will tend to increase muscle mass, good genes gives you more muscle mass and if your calorie deficit is large enough, you will lose large amounts of muscle mass . You can only burn about 500-1000 kcal worth of fat per day, the rest of your deficit will be balanced by breaking down your muscles, and muscles are only about 700kcal/kg compared to 7000kcal/kg in fat, so you lose that mass fast!

  • then what will happen if you stay on small calories deficit for a long time and body fat reaches low percentage?
    – Herokiller
    Commented Apr 16, 2015 at 9:32
  • Well as you lose weight, your calorie need will decrease due to lower body weight and the bodies tendency to favour a certain weight. If you keep the calorie deficit constant, i.e. decrease your intake, your body fat will decrease (although slower and slower), you will get hungrier for the same deficit, making it harder, and eventually you die.
    – Mårten
    Commented Apr 16, 2015 at 10:15
  • You can eat 80% carbs or 0% carbs and be fine. - I'm not sure this is accurate. A diabetic may disagree with you.
    – rrirower
    Commented Apr 16, 2015 at 12:29
  • Yeah but diabetics are not the standard case, they have a disrupted metabolism. Healthy people can eat large amounts of carbs without any problems. The traditional Okinawa diet was 85% carbs and they live to be a 100 years old! As long as we're talking glucose based carbs and not alcohol or fructose, carbs are fine.
    – Mårten
    Commented Apr 16, 2015 at 13:21

You can check this outsanding things to make a perfect diet http://xs.gy/fatburningguide

  • 1
    But don't though...
    – Alec
    Commented Apr 16, 2015 at 18:05

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.